TW201619107A - Liquid crystal compound containing difluoromethoxy bridged bonds and application thereof - Google Patents

Abstract

The invention relates to a liquid crystal compound with a formula I as shown in the specification, wherein R is selected from H and unsubstituted alkyl or alkoxy containing 1-12 carbon atoms or alkyl or alkoxy containing 1-12 carbon atoms with one or more H being substituted by halogens, A1, A2 and A3 are independently selected from a single bond, 1,4-cyclohexylene and 1,4-phenylene, H in the 1,4-phenylene can be independently substituted by one or more halogens, and Z1 and Z2 are independently selected from a single bond or -(CH2)2-. The liquid crystal compound provided by the invention has the characteristics of low rotational viscosity, large dielectric anisotropy, good intersolubility and stable performance, can reduce the driving voltage of a device applying the liquid crystal compound and has broad application prospects.

Description

Liquid crystal compound containing difluoromethoxy bridge and application thereof

The present invention relates to the field of liquid crystal display materials, and in particular to a liquid crystal compound containing a difluoromethoxy bridge and its use.

At present, liquid crystals have been widely used in the field of information display, and at the same time, the application in optical communication has also made some progress (S.T.Wu, D.K.Yang. Reflective Liquid Crystal Displays. Wiley, 2001). In recent years, the application fields of liquid crystal compounds have been significantly expanded to various display devices, electro-optical devices, electronic components, sensors, and the like. For this reason, many different structures have been proposed, and particularly in the field of nematic liquid crystals, nematic liquid crystal compounds have hitherto been most widely used in flat panel displays. Especially in systems for TFT active matrices.

The liquid crystal display has experienced a long development path along with the discovery of liquid crystal. In 1888, the Austrian botanist Friedrich Reinitzer discovered the first liquid crystal material, cholesteryl benzoate. In 1917 Manguin invented the rubbing orientation method for making single domain liquid crystals and studying optical anisotropy. In 1909, E. Bose established the Swarm doctrine and received experimental support from L.S. Ormstein and F. Zernike (1918), followed by De Gennes for statistical ups and downs. G.W.Oseen and H.Zocher founded the continuum theory in 1933 and were perfected by F.C. Frank (1958). M. Born (1916) and K. Lichtennecker (1926) discovered and studied the dielectric anisotropy of liquid crystals. In 1932, W.Kast divided the nematic column into two categories: positive and negative. In 1927, V. Freedericksz and V. Zolinao discovered that nematic liquid crystals were in the electric field. Under the action of (or magnetic field), deformation occurs and there is a voltage threshold (Freederichsz transition). This discovery provides a basis for the production of liquid crystal displays.

In 1968, American RCA company R. Williams discovered that nematic liquid crystals formed fringe domains under the action of electric field and had light scattering. G.H. Heilmeir then developed into a dynamic scattering display mode and made it the world's first liquid crystal display (LCD). In the early 1970s, Helfrich and Schadt invented the TN principle. People used TN photoelectric effect and integrated circuit to make it into a display device (TN-LCD), which opened up a broad prospect for the application of liquid crystal. Since the 1970s, due to the development of large-scale integrated circuits and liquid crystal materials, the application of liquid crystals in display has made a breakthrough. From 1983 to 1985, T. Scheffer et al. proposed Super Twisred Nematic: The STN) mode and the Active Matrix (AM) approach proposed by P. Brody in 1972 were re-used. The traditional TN-LCD technology has been developed into STN-LCD and TFT-LCD technology. Although the number of scan lines of STN can reach more than 768 lines, there are still problems such as response speed, viewing angle and gray scale when the temperature rises. Large-area, high-information, and color displays mostly use active matrix display. TFT-LCD has been widely used in direct-view TVs, large-screen projection TVs, computer terminal displays and some military instrument displays. It is believed that TFT-LCD technology has a broader application prospect.

The "active matrix" includes two types: 1. OMS (Metal Oxide Semiconductor) or other diode on a germanium wafer as a substrate. 2. A thin film transistor (TFT) on a glass plate as a substrate.

Single crystal germanium is used as a substrate material to limit the display size because various parts of the display device and even the module assembly have many problems at their junction. Thus, the second thin film transistor is a promising active matrix type, and the photoelectric effect utilized is usually the TN effect. TFT includes compound Semiconductors, such as Cdse, or TFTs based on polycrystalline or amorphous germanium.

At present, TFT-LCD product technology has matured and successfully solved technical problems such as viewing angle, resolution, color saturation and brightness, and its display performance has approached or exceeded CRT display. Large-size and medium-sized TFT-LCD displays have gradually occupied the mainstream position of flat panel displays in their respective fields. However, due to the limitation of the liquid crystal material itself, the TFT-LCD still has many defects such as not responding fast enough, the voltage is not low enough, and the charge retention rate is not high enough. Therefore, it is particularly important to find a single crystal compound having a low viscosity and a high dielectric anisotropy.

As early as 1989, Merck & Co., Germany, in the US Pat. No. 5,045,229, the liquid crystal compound monomer containing a difluoromethoxy bridge was described, but the desired corresponding compound was not obtained.

In view of the above background, the present invention provides a novel liquid crystal compound having a difluoromethoxy bridge unit structure. The compound has the characteristics of low rotational viscosity, large dielectric anisotropy, good mutual solubility and stable performance, and has the structure I as shown in the formula:

Wherein R is selected from H and unsubstituted or alkyl or alkoxy having _{1 to} 12 carbon atoms in which one or more H is substituted by halogen; and A ₁ , A ₂ and A ₃ are each independently selected from: a bond, 1,4-cyclohexyl, 1,4-phenyl, wherein the hydrogens in the 1,4-phenyl group are each independently substituted by one or more halogens; Z ₁ and Z ₂ are each independently selected from a single bond Or -(CH ₂ ) ₂ -.

Wherein, the liquid crystalline compound of the present invention preferably: R is selected from H and unsubstituted or an alkyl or alkoxy group having 1 to 5 carbon atoms in which one or more H is substituted by halogen; the halogen is a fluorine element a chlorine element, a bromine element, an iodine element, preferably a fluorine element; A ₁ , A ₂ and A ₃ are each independently selected from the group consisting of: a single bond, a 1,4-cyclohexyl group, a 1,4-phenyl group, wherein 1,4- The hydrogen in the phenyl group may each independently be substituted by one or more halogens; the halogen is a fluorine element, a chlorine element, a bromine element, an iodine element, preferably a fluorine element; and Z ₁ and Z ₂ are each a single bond.

The liquid crystal compound of the present invention is further preferably: R is selected from H and unsubstituted alkyl group having 1 to 5 carbon atoms; and A _{1 is} selected from the group consisting of: a single bond, 1,4-cyclohexyl, 1,4-phenyl, Wherein the hydrogen in the 1,4-phenyl group may each independently be substituted by one or more halogens; the halogen is a fluorine element, a chlorine element, a bromine element, an iodine element, preferably a fluorine element; and A ₂ and A ₃ are each independently Selected from: 1,4-cyclohexyl, 1,4-phenyl, wherein the hydrogens in the 1,4-phenyl group are each independently substituted by one or more halogens; the halogen is a fluorine element, a chlorine element, a bromine The element, an iodine element, preferably a fluorine element; Z ₁ and Z ₂ are each a single bond.

And more preferably, the liquid crystal compound is selected from the group consisting of the following structural compounds:

R is selected from an alkyl group having 1 to 5 carbon atoms; as a preferred embodiment of the present invention, the liquid crystal compound is: or

The above compounds have a high dielectric anisotropy and can be applied to the composition to lower the driving voltage of the device.

A second object of the present invention is to provide a method for preparing the above liquid crystal compound containing a difluoromethoxy bridge, and the synthetic route of the preparation method is as follows:

The method comprises the following steps: (a) using compound II-1 as a starting material, reacting with dihydropyran at room temperature with a weak acid (preferably hydrochloric acid) as a catalyst and dichloromethane as a solvent to obtain compound II-2; b) Compound II-2 is protected with nitrogen in tetrahydrofuran as a solvent, reacted with butyllithium at -75 ° C to -85 ° C to form a lithium reagent; and then reacted with methyl iodide to obtain compound II-3; (c) compound II -3 using p-p-toluenesulfonate as a catalyst, stirring and heating to obtain compound II-4; (d) compound II-5 with trifluoromethanesulfonic acid as a catalyst, and 1,3-propanedithiol reflux dehydration, Filtration to give compound II-6; (e) compound II-4 and compound II-6, using triethylamine hydrogen fluoride as a dehydrating agent and bromine as a catalyst to obtain the target compound I; wherein R, A ₁ , A ₂ , A ₃ , Z ₁ and Z _{2 are} as defined above.

The above preparation method can stably obtain a liquid crystal compound containing a difluoromethoxy bridge, and the obtained compound has the advantages of large dielectric anisotropy, good mutual solubility, and stable quality.

Further, the present invention also claims a liquid crystal composition containing a liquid crystal compound of a difluoromethoxy bridge. The liquid crystal compound containing difluoromethoxy bridge is added in a reasonable manner, plus The amount is preferably from 1 to 80%, more preferably from 3 to 50%. It is expected by those skilled in the art that based on the addition of the above liquid crystal compound, the dielectric anisotropy of the conventional liquid crystal composition can be further improved, and the technical effect of lowering the driving voltage of the device can be obtained.

Still another object of the present invention is to protect the above liquid crystal compound containing a difluoromethoxy bridge and a composition thereof in the field of liquid crystal display.

Specifically, the use of the above compound or composition in a liquid crystal display device includes, but is not limited to, a TN, ADS, FFS or IPS liquid crystal display. When the liquid crystal composition is applied to a liquid crystal display device, there is an advantage that the driving voltage is lowered.

The abbreviations of the performance test parameters in the present invention are as follows: Δ ε represents dielectric anisotropy at 25 ° C and 1 kHz; γ 1 represents rotational viscosity at 25 ° C (mPa.s); Δn is optical orientation The opposite is true, no is the refractive index (589nm, 25 ° C); Cp is the clearing point (°C) of the liquid crystal composition; VHR charge retention rate (%): the mixed liquid crystal is injected into the liquid crystal cell, placed in the incubator, and the temperature is stable. After that, enter the test program and manually take the point to get the charge retention rate value. The measurement voltage is 5V, the power-on time is 5ms, and the holding time is 500ms.

Example 1:

4-[(3,4,5-Trifluoro-2-methyl-phenoxy)-difluoromethyl]-3,5,2'-trifluoro-4"-propyl-[1,1' Synthesis of 4',1"] terphenyl (compound 7)

1) Synthesis of 2-(3,4,5-trifluoro-phenoxy)-tetrahydropyran (Compound 2)

Add 500g of 3,4,5-trifluorophenol, 72g of 2,3-dihydropyran, 140ml of dichloromethane to 500ml dry clean three-necked bottle, stir, slowly add 5 drops of concentrated hydrochloric acid at room temperature, drop the chamber The temperature was reacted for 3 hours. The reaction solution was washed twice with a 10% aqueous sodium hydroxide solution (100 ml × 2), dried over 20 g of anhydrous sodium sulfate for 30 min, filtered, and then evaporated.

2) Synthesis of 2-(3,4,5-trifluoro-2-methyl-phenoxy)-tetrahydropyran (Compound 3)

Add 1 g of 2-(3,4,5-trifluoro-phenoxy)-tetrahydropyran (Compound 2) to a 1 L dry clean three-necked flask, 500 ml of tetrahydrofuran, protect with nitrogen, and cool the liquid nitrogen to -75 °C~- At 85 ° C, add 200ml of butyl lithium, drop the temperature control reaction for 1h, add 89g of methyl iodide, drop, control temperature -75 ° C ~ -85 ° C reaction for 30 minutes, then naturally warm to -20 ° C, with ammonium chloride The aqueous solution is hydrolytically destroyed. Liquid separation, The aqueous phase was extracted twice with 100 ml of 2 ethyl acetate. The organic phase was combined, and the organic phase was washed twice with 100 ml of sodium chloride aqueous solution and dried over 30 g of anhydrous sodium sulfate for 30 min. A white solid was obtained.

Theoretical yield: 102 g, actual yield: 64 g, yield: 62.7%, white solid, GC: 99.6%, m.p.: 67.65.

3) Synthesis of 3,4,5-trifluoro-2-methyl-phenol (Compound 4)

10 g of dry clean three-necked vial was charged with 10 g of 2-(3,4,5-trifluoro-2-methyl-phenoxy)-tetrahydropyran (compound 3), 2 g of pyridinium p-toluenesulfonate, 50 ml of ethanol, The mixture was heated to 60 ° C to 70 ° C with stirring, and the reaction was timed for 3 hours. The reaction solution was sparged, 20 ml of dichloromethane was added, and the product was dissolved, washed twice with 10 ml of aqueous sodium chloride solution, dried over 10 g of anhydrous sodium sulfate and dried.

Theoretical yield: 6.5 g, actual yield: 6.5 g, yield: 100% (by theory), colorless liquid, GC: 99.155%.

4) Synthesis of yttrium trifluoromethanesulfonate (Compound 6)

137g of 3,5,2'-trifluoro-4"-propyl-[1,1';4',1"]terphenyl-4-carboxylic acid (Compound 5), 47mL 1,3-propane was added to a 1L three-necked vial Dithiol, 42 mL of trifluoromethanesulfonic acid, 145 mL of toluene and 145 mL of isooctane was installed, and a water separator was installed at one side. The temperature was raised to reflux, and the reaction was carried out for 6 hours, and the mixture was slowly cooled to 0 ° C, and suction filtered to give a solid. After drying, the next step is carried out.

5) 4-[(3,4,5-Trifluoro-2-methyl-phenoxy)-difluoromethyl]-3,5,2'-trifluoro-4"-propyl-[1, Synthesis of 1';4',1"] terphenyl (compound 7)

200 mL of dichloromethane, 39 mL of triethylamine and 45.4 g of 3,4,5-trifluoro-2-methyl-phenol (Compound 4) were added to a 2 L three-necked flask, and the temperature was lowered to 20 ° C, and 142 g of trifluoromethylsulfonate was added. A solution of the phosphonium salt (Compound 6) and 400 mL of dichloromethane was stirred for 1 hour. After the temperature was controlled to -75 ° C, 77 g of triethylamine hydrogen fluoride was added dropwise, and stirring was continued for 1 hour. Temperature control - below 75 ° C, a solution consisting of 15 mL of bromine and 30 mL of dichloromethane, after warming to -10 ° C, post-treatment. In a 10L bucket, add 1L of water, start stirring, pour the reaction solution, stir for a few minutes, slowly add sodium bicarbonate solid (produce a large amount of gas) to the solution PH near neutral, static liquid separation, the aqueous phase is extracted with 500ml of dichloromethane Once, the organic phases were combined, and the solvent was evaporated to dryness crystals eluted eluted eluted eluted with Theoretical yield: 128.6 g, actual yield: 103 g, yield: 80.0%, gas phase purity (GC): 99.9%, melting point: 70.9 ° C, Δn is 0.197, Δ ε is 31.5, γ 1 is 208 mPa. s.

Mass spectrometry fragmentation: 173, 346, 375, 536 (molecular ion peak); H-NMR nuclear magnetic resonance spectrum (CDCl3, 300 MHz): δ H: 0.90-2.60 (m, 10H), 6.10-7.60 (m, 10H) .

Example 2:

Synthesis of 4-[(3,4,5-trifluoro-2-methyl-phenoxy)]-difluoromethyl-3,5-difluoro-4'-propylbiphenyl (Compound 10)

1) Synthesis of ytterbium triflate (compound 9)

A 1 L three-necked flask was charged with 102 g of 4'-propyl-3,5-difluorobiphenylcarboxylic acid (Compound 8), 47 mL of 1,3-propanedithiol, 42 mL of trifluoromethanesulfonic acid, 145 mL of toluene and 145 mL of isooctane. A water separator was installed at one side, heated to reflux, reacted for 6 hours, slowly cooled to 0 ° C, and suction filtered to give a solid. After drying, the next step is carried out.

2) 4-[(3,4,5-Trifluoro-2-methyl-phenoxy)]-difluoromethyl-3,5-difluoro-4'-propylbiphenyl (Compound 10) synthesis

2mL three-necked bottle was added with 200mL of dichloromethane, 39mL of triethylamine and 45.4g of 3,5- Difluoro-4-(3-fluoropropoxy)-phenol (Compound 4), cooled to 20 ° C, and added a solution consisting of 117 g of yttrium trifluoromethanesulfonate (Compound 10) and 200 mL of dichloromethane, stirred 1 hour. After the temperature was controlled to -75 ° C, 77 g of triethylamine hydrogen fluoride was added dropwise, and stirring was continued for 1 hour. Temperature control - below 75 ° C, a solution consisting of 15 mL of bromine and 30 mL of dichloromethane, after warming to -10 ° C, post-treatment. In a 10L bucket, add 1L of water, start stirring, pour the reaction solution, stir for a few minutes, slowly add sodium bicarbonate solid (produce a large amount of gas) to the solution PH near neutral, static liquid separation, the aqueous phase is extracted with 500ml of dichloromethane Once, the organic phases were combined, and the solvent was evaporated to dryness eluted eluted eluted elute Theoretical yield: 106 g, actual yield: 69 g, yield: 65.1%, gas phase purity (GC): 99.9%, Δn is 0.109, Δε is 23.0, and γ 1 is 52.1 mPa. s.

Mass spectrometry fragment: 252, 281, 442 (molecular ion peak); H-NMR nuclear magnetic spectrum (CDCl3, 300 MHz): δ H: 0.90-2.60 (m, 10H), 6.10-7.50 (m, 7H).

Example 3:

4-[(3,4,5-trifluoro-2-methyl-phenoxy)]-difluoromethyl-2',3,5-trifluoro-4'-propylbiphenyl (compound 13) Synthesis

1) Synthesis of sulfonium trifluoromethanesulfonate (Compound 11)

1L three-necked flask was added with 65g of 4'-propyl-2',3,5-trifluorodibenzoic acid (Compound 11), 28mL of 1,3-propanedithiol, 25mL of trifluoromethanesulfonic acid, 90mL of toluene and 90mL of different Octane, a water separator was installed at one side, heated to reflux, reacted for 6 hours, slowly cooled to 0 ° C, and suction filtered to give a solid. After drying, the next step is carried out.

2) 4-[(3,4,5-Trifluoro-2-methyl-phenoxy)]-difluoromethyl-3,5-difluoro-4'-propylbiphenyl (Compound 10) synthesis

100 mL of dichloromethane, 20 mL of triethylamine and 23 g of 3,5-difluoro-4-(3-fluoropropoxy)-phenol (Compound 4) were added to a 1 L three-necked flask, and the temperature was lowered to 20 ° C, and 60.6 g of trifluoroethylene was added. A solution of sulfonium methanesulfonate (Compound 11) and 100 mL of dichloromethane was stirred for 1 hour. After the temperature was controlled to -75 ° C, 38 g of triethylamine hydrogen fluoride was added dropwise, and stirring was continued for 1 hour. Temperature control - below 75 ° C, a solution consisting of 8 mL of bromine and 15 mL of dichloromethane was post-treated after warming to -10 °C. In a 5L bucket, add 0.5L of water, start stirring, pour the reaction solution, stir for a few minutes, slowly add sodium bicarbonate solid (produced a large amount of gas) to the solution PH near neutral, static liquid separation, the aqueous phase is extracted once with 250ml of dichloromethane, the organic phase is combined, the solvent is dried at 70 ° C to obtain a viscous material, using 2 times ethanol and 0.5 times petroleum ether Recrystallize three times and filter dry to dry a white solid. Theoretical yield: 60.6 g, actual yield: 38.2 g, yield: 63%, gas phase purity (GC): 99.9%, Δn is 0.090, Δε is 26.5, and γ1 is 59.8 mPa. s.

Mass spectrometry fragmentation: 270, 299, 460 (molecular ion peak); H-NMR nuclear magnetic resonance spectrum (CDCl3, 300 MHz): δ H: 0.90-2.60 (m, 10H), 6.10-7.50 (m, 6H).

Example 4-17

According to the technical scheme of Examples 1-3, the following compounds can be synthesized by simply replacing the raw materials containing the corresponding groups (the specific preparation method does not need substantial adjustment):

Example 18 Mixed Crystal Composition

The liquid crystal monomers used in the following compositions were all supplied by Beijing 800 Million Time Liquid Crystal Technology Co., Ltd. The content of each component in the examples represents the percentage of quality unless otherwise specified.

The following parts by weight of the liquid crystal compound were taken and a liquid crystal composition was prepared. The specific ratios and the performance parameters of the obtained liquid crystal composition are shown in the following table.

The application of the liquid crystal compound having a difluoromethyl ether bridge structure in the TN, IPS, FFS, and ADS-TFT modes, and the results are shown in Tables 1 to 3.

It can be seen from Tables 1-5 that a liquid crystal composition in which a compound of the present invention is directly added or a compound of the present invention is used in place of a conventional dielectric anisotropic compound (Compound 14) has a moderate rotational viscosity, a moderate Δn value, and a charge retention ratio. High, especially with a large dielectric anisotropy. Meanwhile, the liquid crystal composition of the present invention, wherein the compound is added in an amount of from 1 to 80%, more preferably from 2 to 50%.

In addition to the composition exemplified in the test examples, the addition of the other provided by the present invention has two Other liquid crystal compositions of liquid crystal compounds having a fluoromethyl ether bridge structure can obtain equally excellent optical and electrical properties.

Although the present invention has been described in detail above with the aid of the general description, the specific embodiments and the examples of the invention, it may be obvious to those skilled in the art . Therefore, such modifications or improvements made without departing from the spirit of the invention are intended to be within the scope of the invention.

Claims (18)

A liquid crystal compound containing a difluoromethoxy bridge, which has a structure as shown in Formula I: Wherein R is selected from H and unsubstituted or alkyl or alkoxy having _{1 to} 12 carbon atoms in which one or more H is substituted by halogen; and A ₁ , A ₂ and A ₃ are each independently selected from: a bond, 1,4-cyclohexyl, 1,4-phenyl, wherein the hydrogens in the 1,4-phenyl group are each independently substituted by one or more halogens; Z ₁ and Z ₂ are each independently selected from a single bond Or -(CH ₂ ) ₂ -. The compound according to claim 1, wherein R is selected from H and an unsubstituted or alkyl or alkoxy group having 1 to 5 carbon atoms in which one or more H is substituted by halogen; a fluorine element, a chlorine element, a bromine element, an iodine element, preferably a fluorine element; A ₁ , A ₂ and A ₃ are each independently selected from the group consisting of a single bond, a 1,4-cyclohexyl group, a 1,4-phenyl group, wherein 1, The hydrogen in the 4-phenyl group may each independently be substituted by one or more halogens; the halogen is a fluorine element, a chlorine element, a bromine element, an iodine element, preferably a fluorine element; and Z ₁ and Z ₂ are each a single bond. The compound according to claim 1 or 2, wherein R is selected from H and unsubstituted alkyl group having 1 to 5 carbon atoms; and A _{1 is} selected from the group consisting of: a single bond, 1,4-cyclohexyl, 1,4-phenyl, wherein the hydrogens in the 1,4-phenyl group are each independently substituted by one or more halogens; the halogen is a fluorine element, a chlorine element, a bromine element, an iodine element, preferably a fluorine element; ₂ and A ₃ are each independently selected from the group consisting of: 1,4-cyclohexyl, 1,4-phenyl, wherein the hydrogens in the 1,4-phenyl group are each independently substituted by one or more halogens; Fluorine element, chlorine element, bromine element, and iodine element are preferably fluorine elements; Z ₁ and Z ₂ are each a single bond. The compound according to claim 3, wherein the halogen is a fluorine element. The compound according to claim 1, wherein the liquid crystal compound is selected from the group consisting of the following structural compounds: Wherein R is selected from alkyl groups having 1 to 5 carbon atoms. The compound according to claim 5, wherein said liquid crystal compound is: A process for the preparation of a compound according to any one of claims 1, 2 or 4-6, characterized in that the synthetic route is as follows: Specifically, the method comprises the following steps: (a) using compound II-1 as a starting material, using weak acid as a catalyst, dichloromethane as a solvent, and reacting with dihydropyran at room temperature to obtain compound II-2; (b) compound II -2 using tetrahydrofuran as a solvent, protecting with nitrogen, reacting with butyllithium at -75 ° C to -85 ° C to form a lithium reagent; reacting with methyl iodide to obtain compound II-3; (c) compound II-3 Pyridinium tosylate is used as a catalyst, and the reaction is stirred and heated to obtain a compound II-4; (d) the compound II-5 is trifluoromethanesulfonic acid as a catalyst, refluxed with 1,3-propanedithiol, and filtered to obtain a compound II. -6; (e) compound II-4 and compound II-6, using triethylamine hydrogen fluoride as a dehydrating agent and bromine as a catalyst to obtain the target compound I; wherein R, A ₁ , A ₂ , A ₃ , Z ₁ and Z _{2 are} as defined. A process for the preparation of a compound according to claim 3, characterized in that the synthetic route is as follows: Specifically, the method comprises the following steps: (a) using compound II-1 as a starting material, using weak acid as a catalyst, dichloromethane as a solvent, and reacting with dihydropyran at room temperature to obtain compound II-2; (b) compound II -2 using tetrahydrofuran as a solvent, protecting with nitrogen, reacting with butyllithium at -75 ° C to -85 ° C to form a lithium reagent; reacting with methyl iodide to obtain compound II-3; (c) compound II-3 Pyridinium tosylate is used as a catalyst, and the reaction is stirred and heated to obtain a compound II-4; (d) the compound II-5 is trifluoromethanesulfonic acid as a catalyst, refluxed with 1,3-propanedithiol, and filtered to obtain a compound II. -6; (e) compound II-4 and compound II-6, using triethylamine hydrogen fluoride as a dehydrating agent, bromine as a catalyst, the reaction to obtain the target compound I; wherein, R, A ₁ , A ₂ , A ₃ , Z ₁ and Z _{2 are} as defined. A liquid crystal composition containing the liquid crystal compound according to any one of claims 1, 2 or 4-6. A liquid crystal composition containing the liquid crystal compound according to claim 3. The composition according to claim 9, wherein the liquid crystal compound is added in an amount of from 1 to 80%, preferably from 3 to 50%. The composition according to claim 10, characterized in that the liquid crystal compound is added in an amount of from 1 to 80%, preferably from 3 to 50%. The use of the liquid crystal compound according to any one of claims 1, 2 or 4 to 6 in the field of liquid crystal display. The use of the liquid crystal compound according to claim 3 in the field of liquid crystal display. Use of the composition of claim 9 in the field of liquid crystal display. Use of the composition of claim 10 in the field of liquid crystal display. Use of the composition of claim 11 in the field of liquid crystal display. Use of the composition of claim 12 in the field of liquid crystal display.